Manufacture of shoes



July 2, 1940. E. H. wooDBERRY INUFACTURE 0F SHES Filed lay 26, 1939 2Sheets-Sheet 1 Patented July 2, 1940 UNITED STATES PATENT oFF-ICE:,zoazis MANUFAcTUaE oF snoEs Application May 26, 1939, Serial No.275,812

2 `(Zlaiins. (Cl. 12-142) In the manufacture of shoes the addition ofmoisture is necessary in order that the shoes be in the correct temper,i. e., the prciper degree of softness, flexibility and workability, foreach operation ln the process of manufacture. Inasmuch as succeedingoperations of manufacture require progressively drier leather, the shoesare moistened at the beginning of the manufacture and themoisturecontent thereiniis reduced by partially drying the leather aftersuch operations as stretchingthe upper over the last, attaching the soleto the lasted upper, pressing or leveling the sole, attaching the heel,edge and heel-making, bottom sanding, etc., until toward the end of 5the process, before bottom nishing, the leather should be practicallydry to be in correct temper.

The importance of having the shoe in the correct temper, neither too wetnortoo dry, at any particular operation cannot be overemphasizedinasmuch as on its particular condition depends the shape and fit of theupper, the form and tread of the sole, the smoothness and regularity ofthe edge and the quality and uniformity of the bottom. i :5` The usualpractice in the past has been to allow the shoes to remain on dryingracks open to the atmosphere or in crude dry houses until the shoeslooked or seemed to be in the proper temper. However, the procedurerequired so much ;0 floor space and time in process and resulted insuch,` an accumulation of work in process that modern manufacturing andmarketi g conditions have made artificial drying necessa y. Also, owingto variation in atmospheric humidity, work often too wet or too dry forproper operation, with a consequent detriment to the quality of thefinished shoes. It has been proposed to sub- L0 stitute dehumidified airfor atmospheric air in the drying stages, flowing the air throughtunnels insure a positive drying system by which the` shoes arepresented to the workmen in the correct temper automatically withoutdepending on is`- fallible human determination,` to allow for the inprocess, and the inaccuracy of human determination of the correcttemper. the shoes were uncontrolled drying which inevitably takes placeWhile work operations are being performed between successive dryingstages, and to accomplish the foregoing positively, automatically andconstantly day after day regardless of variations in humidity andtemperature of atmospheric air. According to this invention a detailedsurvey of each particular factory is made prior to installation of theequipment. The results of the survey determine the exact moisturecontent required in 19 the shoe at each point in the process, the normalrate of moisture loss `in open air during the normal fabrication of theshoe, and al1 this at any particular set of atmospheric conditions. Thusthe points at which artificial drying must be introduced and the amountsof moisture that must be removed at each point with any particular setof atmospheric l conditions are determined. Knowing the rate of dryingand the amount of moisture that must be removed at any point in 20 theprocess, itis a simple matter to compute the correct drying time for theparticular atmospheric conditions under which the tests are made. Theproblem then resolves itself into setting up a system that will keep thepredetermined g5 rate of drying relatively constant as atmosphericconditions vary. To do this I determine corrective factors correspondingto various combinations of atmospheric temperature and relative humidityfor controlling the degree of moisture removal in each dryer. I thenregulate the extent of drying in each dryer according to thosepredetermined corrective factors which correspond to the then existingatmospheric temperature and relative humidity, thereby insuring that theshoes leave the dryer in the same degree of temper regardless ofatmospheric conditions.

The extent of drying may be regulated in various ways as by varying thetime of drying or the velocity of the air through the dryer. However, 40in most cases it is preferable to hold the drying time and air velocityconstant and to control the drying effect by regulating the temperatureof the air in the dryers. To indicate the correct temperature of the airin each dryer correspond- 5 ing to each combination of atmospherictemperature and relative humidity I prepare a chart for each dryer, eachchart comprising vertical and horizontal rows corresponding to differentatmospheric temperatures and relative humidities. Thus, if the verticalrows correspond to different atmospheric temperatures, the horizontalrows correspond to different degrees of relative humidity. To regulate adryer the then existing temperature and relative humidityr of u theatmosphere are determined with an ordinary thermometer and humidostatand the operator locates on the chart the vertical and horizontalcolumns corresponding to then existing atmospheric temperature andrelative humidity. At the intersection of the two columns. he finds thenumber which indicates the proper setting of the dryer under thoseconditions of atmospheric temperature and relative humidity. The numberson the chart may indicate the air temperatures in the dryer or they maybe merely arbitrary figures which indicate how the dryer regulatorshould be set.

The numbers on the chart involve corrective factors by which the dryingeifect may be maintained constant under different atmosphericconditions. In general the corrective factors involve an increase ofdryer temperature with an increase of either atmospheric temperature oratmospheric humidity and vice versa for each dryer.

Changes in atmospheric conditions influence the drying of the shoes invarious ways. The principal effect is to vary evaporation from theshoes. 'Ihus on a humid day the evaporation would ordinarily be slowerthan on a dry day (other conditions remaining the same). A secondaryeifect is to vary the rate of drying dury ing the operating intervalsbetween the drying stages since, while a particular operation is beingperformed, the shoes are slowly drying in the open air. On a humid daythis drying is retarded and consequently more moisture must be removedin the succeeding drying stage to afford the proper temper for the nextoperation. For this reason the aforesaid corrective factors preferablyinclude a correction for variations in open-air drying under differentatmospheric conditions.

Varying the temperature of the air in each dryer introduces stillanother variable, namely, a variation in the rate at which moisturefeeds to the surface of the leather while in the dryer. The hotter theleather the faster the moisture moves to the surface of the leather tobe carried away by the heated air in the dryer. Hence, as the humidityof the atmosphere increases the temperature in the dryer need not beincreased as much as it would be if the capillary feed of moisture tothe surface of the leather were unaected by increase of temperature inthe dryer. Thus the aforesaid corrective factors include corrections forthe variation in rate at which moisture moves to the surface of the shoematerial in response to temperature changes.

In the accompanying drawings:

Fig. 1 illustrates diagrammatically a typical dryer:

Fig. 2 shows a control unit for-the temperature of the air supplied tothe dryer;

Fig. 3 shows a typical chart by which the setting of the control unit isdetermined; and

Fig. 4 illustrates a temperature-relative humidity diagram by which thechart is prepared.

'Ihe shoes in process are advanced through the tunnel I of the dryershown in Fig. 1 by a conveyor il driven at a pre-selected rate of speedby suitable means (not shown). A stream of air is set up in the tunnelby a blower l5 which draws air from the room and passes it over a heaterI6 and through a conduit I1 into the tunnel I0. 'Ijhe speed of the airstream so set up is determined bythe blower and held at that uniformrate previously found to be most efiiclent.

The heater il may be of any desired type, preferably steam or electric,and is regulated by a control unit 2li. The structure of this unit isnot shown in detail since it may be varied to suit conditions. 'I'hecontrol unit 20 includes a panel 25, shown in Fig. 2, upon which ismounted a dry bulb thermometer 26 and a humidostat 21. The readings ofthese instruments give the temperature and relative humidity of the airas it enters the dryer.

Also mounted on the panel are a chart 28 and a regulator switch 29. Thechart 28 (Fig. 3) embodies a plurality of vertical columns 30 eachheaded by a temperature reading and a plurality of horizontal columns 3leach headed by a relative humidity reading. The columns 30 and 3l crossto define a plurality of squares 32 in which are placed numbers whichindicate the setting of the switch 29 that regulates the temperature [ofthe drying air stream in the tunnel I0.

'I'he numbers in the squares 32 are determined from thetemperature-relative diagram set forth in Fig. 4. Such a diagram is onewith which engineers in the drying field are familiar and is here shownso that the procedure by which these numbers are determined will beclear to one skilled in this art.

The maximum rate of drying of leather, or in other words the minimumpercent of humidity of the drying air varies with the tannage and cut ofthe leather. It will be here assumed that for the leather to be treatedthe drying air must have a humidity of at least Selecting theatmospheric conditions generally prevailing in the particularl localityin which the dryer is to be used, e. g. a dry bulb temperature of 70 anda relative humidity of 41% I locate the point 50 on the 15% relativehumidity line. It is essential that the rate of drying be held constantalthough the temperature may vary and, as pointed out above, suchvariance in temperature affects the drying of the leather in tworespects. First, the rate of diffusion of the moisture from within theleather increases with the temperature. Second, the rate of dryingoutside the dryer increases with the temperature and consequently theamount of additional drying necessary within the dryer to maintainuniform temper of the leather decreases. These factors for the leatherto be dried are represented by the sloped lines 5I and 52 drawn throughthe point 50.- The lines 5l and 52 thus represent the corrective factorsinvolved in the determination of the numbers in the squares I2. 'Ihealgebraic sum of these factors is the line il drawn through the point 50so that this line represents the composite corrective factors and isused in the determination of the numbers as will now be described.

I will consider first a condition where the atmosphere has a dry bulbtemperature oi' 80 and relative humidity of 50% and find the point I5 atthe intersection of those lines on Fig. 4. From that point 55 is drawn ahorizontal line 56 which intersects successively lines on the diagram atpoints 51, 58, 59 and 60. A vertical line from the point 58 at which thehorizontal line 56 crosses the composite corrective factor line 53crosses the temperature line at IIB, and

lthat number is inserted in the square 32 common to an atmosphere of 80temperature and 50% humidity.

The other numbers on the chart Il are similarly derived and a chartprepared for the particular dryer under consideration. Obviously changesin the amount of moisture to be extracted from the shoes, the length ofthe dryer, the speed of travel of the shoes through the dryer, thevelocity of the drying air, the relative humidity to be maintained inthe dryer, the tannage and out of the leather, etc. require that a chartbe prepared for each dryer. Once prepared, however, the dryer canreadily be regulated so that the shoes traveling therethrough arepresented to the operating station associated with that dryer in thedesired temper regardless of atmospheric conditions.

While this invention has been -shown and described in connection with asingle installation, it will be understood that it is not limitedthereto but is applicable to. other installations and uses within thespirit and scope of the invention as set forth in the following claims.

I claim:

1. The process of manufacturing shoes which comprises wetting shoeparts, assembling the shoes at aseries of successive operation periodsin the open air and with air dryers removing portions of the moisturebetween two adjacent operations, characterized by determining undernormal atmospheric humidity and temperature conditions the amount ofmoisture normally lost in the manufacturing process through the first oftwo open air operation periods, determining the amount of additionalmoisture which must be removed before the second operation can be'properly performed, determining the drying time-necessary to remove thisadditional moisture under average temperature conditions in a dryerwithv high uniform velocity, and then, with the artiilcial drying timeand air velocity xed, so varying the drying temperature and consequentlythe drying air relative humidity, as atmospheric humidity andtemperature conditions change, that the total moisture removed in theopen air operation and the drying periods is always constant, therebytaking into account the eiect-of changing temperatures upon the rate ofdiiusion of the moisture out f the leather. y

2. In that process of making shoes which comprises wetting shoe parts,assembling the shoes at a series of successive operations performed inatmospheric air, and introducing an atmospheric air dryer into saidseries of operations, the steps of determining the average amount ofmoisture normally lost during the manufacturing operations in theatmospheric air prior to the dryer, determining the amount of additionalmoisture which must be removed by said dryer to insure that the shoes beat the temper best suited for the operation next following the dryer,deter-- mining the drying time necessary to remove such additionalmoisture under average temperature conditions and then, while holdingthe dryer time xed, so regulating the temperature of the atmospheric airin the dryer in a predetermined manner that the total amount of moisturere; moved in the atmospheric air operations and in the dryer isalways-constant.

EDWARD H. WOODBERRY.

